Alyssa Madge, who has been growing her hair all her life, is helping the Little Princess Trust, which makes wigs for sick children.
The Sandye Place Academy student’s hair currently falls to just above her waist but it will cut back by 14 inches or 36cm to a little below her shoulders.
Alyssa’s mother, Tasha Madge, said: “It’s quite a big cut and she’s been growing it since she was little.
“I had hair very similar as a child and when I had it cut I cried. Alyssa’s been asking to have it cut since she was five but every year I’ve put it back because of this.
“This year she watched Children in Need and said about her hair again and doing it for a good cause.”
Alyssa, of Maple Road in Sandy, has had to go to hospital with back problems a few times recently so Tasha thought this would give her a pick-me-up.
Tasha searched for a children’s cause and discovered the Little Princess Trust, who then sent a fundraising pack.
The charity provides real hair wigs for children who have lost their hair as a result of cancer.
Alyssa will be following in the footsteps of singer, Jessie J, who donated her hair to the cause.
She will be giving twice the minimum seven inch donation. Alyssa, who is a member of Sandy Saxon Cubs, has only ever had it trimmed before.
The family’s hairdresser, Hannah Wigley, will do the job at the Sandy scout headquarters on Sunday, December 22.
Tasha added: “It will make a little boy or girl’s new year.”
You can donate online by visiting http://uk.virginmoneygiving.com/ and searching for Alyssa Madge. Then click on Alyssa Madge’s Rapunzel Challenge.
Not only will Alyssa’s hair go to the charity but also any donations that are made. The total stands at more than £100 so far.